Radiation Hardness of LSI/VLSI Fabrication Processes

Candidate large-scale and very large scale integrated (LSI/VLSI) circuit fabrication processes have been partitioned, and representative MOS capacitors irradiation-bias stressed and characterized. Laser annealing for implantation activation of polysilicon films has been found to provide MOS devices with greater radiation-hardness than those which are furnace annealed. Pre-gate processes (those processes performed before the deposition of the gate-electrode, which is either aluminum or polysilicon) involving ionizing radiation, such as X-ray lithography, cause increased MOS irradiation-bias sensitivities, even though post-fabrication, pre-irradiation characteristics reveal no differences from standard, non-radiative processing. These deleterious effects can be eliminated when both high temperature (800°C) pre-gate annealing and aluminum sintering (450°C) operations are performed. Since the aluminum sintering operation releases atomic hydrogen into the gate oxide, reducing the radiation damage, other oxide hydrogenation techniques may prove beneficial for those cases where aluminum is not available, such as in polysilicon gate structures.